Allen County
I bet you think you've died and gone to Nature Preserve heaven. Yes, Allen County, which is almost entirely made up of Fort Wayne, has quite a few preserves and parks, some of them spectacular, and all showing that the county is both populated and governed by people who have some concern for the environment and natural areas. This makes up for the fact that Fort Wayne (from what I've seen of it) is kind of a blah city.
Arrowhead Marsh/Arrowhead Prairie
Herman F. Hammer Wald Nature Preserve
Little Cedar Creek Nature Preserve